How to Tell if Your Furnace Has a Pilot Light

The presence of a pilot light affects furnace operation, troubleshooting, and safety. This article explains clear ways to determine whether a furnace uses a pilot light, signs to watch for, how to check safely, and when to call a professional. It helps homeowners and renters identify ignition types and decide next steps for repair or maintenance.

Feature	Pilot Light Furnace	Electronic Ignition Furnace
Ignition Visible	Yes (small flame in burner area)	No (spark or hot surface igniter)
Energy Use When Off	Uses small gas constantly	No standby gas use
Common Age	Older systems	Newer systems (post-1990s)
Relight Needed After Outage	Often manual relight	Auto-reignite

How Pilot Lights And Ignition Systems Differ

Furnaces use one of two primary ignition systems: a continuous pilot light or an electronic ignition (standing pilot vs. intermittent ignition). A pilot light is a small, continuously burning flame that lights the main burners. An electronic ignition uses a spark or hot surface element to light burners only when heat is required, improving efficiency.

Understanding the difference provides context for identifying whether a furnace has a pilot light and informs safety and maintenance decisions.

Signs A Furnace Likely Has A Pilot Light

Several observable and operational clues indicate the presence of a pilot light. Checking these signs helps avoid unnecessary disassembly and reduces risks.

• Older Furnace Age: Furnaces installed before the 1990s often used pilot lights.
• Continuous Gas Smell When Off: While any gas smell is a leak risk, pilot-equipped furnaces may have a faint constant odor if the area is unventilated; immediate safety checks are required for any gas odor.
• Manual Relight Requirement: If the furnace needs manual relighting after a power outage or interruption, it likely has a pilot light.
• Visible Flame Window: Many pilot systems have a small viewport or access panel where the pilot flame is visible.
• Gas Valve With “Pilot” Setting: The gas control knob often has positions labeled “Off,” “Pilot,” and “On.”

Step-By-Step Safe Check: How To See If There’s A Pilot Light

Before performing any checks, prioritize safety. If gas odor is present, evacuate and call the gas company or emergency services. Do not light matches or operate electrical switches.

1. Turn Off Power: Shut off the furnace power at the service switch or circuit breaker to prevent blower activation or ignition cycles while inspecting.

2. Locate The Furnace: Most residential furnaces are in basements, utility closets, garages, or attics. Identify the access panel and the gas control area.

3. Find The Gas Control Knob: Look for a control assembly with labels like “Pilot,” “On,” and “Off.” This is a strong indicator of a pilot-light system.

4. Look For A Small Flame Or Viewing Port: Remove the lower panel carefully and check for a small blue flame near the burner assembly or through a small port. Use a flashlight rather than a match or lighter.

5. Read The Furnace Label: Manufacturer labels often specify ignition type under specifications or troubleshooting sections.

How To Relight A Pilot Light (If Equipped)

If the furnace has a pilot light and it went out, relighting may restore function. Follow the furnace manual instructions or the general safe procedure below. If unsure, call a professional.

1. Turn Gas Control To Off: Wait five to ten minutes to clear any residual gas.

2. Set The Gas Control To Pilot: Depress and hold the pilot button while lighting, following the manufacturer direction.

3. Light With Match Or Lighter: Use a long lighter or match through the access port. Keep holding the pilot button for 20–60 seconds to allow the thermocouple to heat.

4. Switch To On: If the pilot stays lit, turn the gas knob to the “On” position and restore power.

5. Observe Operation: Allow the furnace to cycle and confirm the main burners ignite correctly.

Note: Do not attempt relighting if a strong gas odor is present. Evacuate and call the gas company.

Signs The Furnace Uses Electronic Ignition Instead

Electronic ignition systems eliminate the constant pilot flame. Indicators include: no visible pilot flame, presence of a spark module or hot surface igniter, no gas control knob labeled “Pilot,” and automatic ignition on call for heat without manual relighting after power interruption.

Modern furnaces may use either a hot surface igniter (HSI) or an intermittent pilot/spark ignition module. Both types are designed for greater efficiency and safety.

Safety Warnings And Precautions

Working around gas appliances has inherent risks. Homeowners should prioritize safety and consider contacting qualified HVAC technicians for inspection and repairs.

• Any Gas Smell Requires Immediate Action: Evacuate, avoid using electrical devices, and call emergency services or the gas utility.
• Do Not Tamper With Gas Lines: Adjustments to gas valves, regulators, or piping should be performed only by licensed professionals.
• Use The Furnace Manual: Manufacturer instructions provide model-specific guidance on locating and relighting pilot lights and troubleshooting ignition.
• Schedule Regular Maintenance: Annual professional tune-ups help ensure safe operation whether the furnace uses a pilot light or electronic ignition.

When To Call An HVAC Professional

Problems that require a technician include persistent pilot outages, thermocouple or thermopile failures, gas valve issues, pilot light flicker, or suspected carbon monoxide leaks. Technicians can also convert older pilot systems to modern electronic ignition for efficiency gains.

Calling a professional is advised if the homeowner is uncomfortable performing the safe checks or relighting, or if relighting fails.

Common Pilot Light Problems And Likely Causes

Understanding frequent issues helps identify whether relighting is a short-term fix or a sign of larger problems.

Symptom	Possible Cause	Recommended Action
Pilot Won’t Stay Lit	Faulty thermocouple/thermopile or dirty pilot orifice	Clean pilot orifice; replace thermocouple; call technician
Pilot Light Is Weak Or Yellow	Insufficient gas pressure or dirty burner	Inspect/clean burner; check gas pressure; professional service
Pilot Goes Out Frequently	Drafts, vibration, thermocouple issues, or gas supply interruption	Eliminate drafts, secure assembly, replace components, call pro
Strong Gas Odor After Pilot Goes Out	Gas escaping when valve open	Ventilate, evacuate, call gas company or emergency services

Converting From Pilot Light To Electronic Ignition

Many homeowners consider converting an older pilot-light furnace to electronic ignition to improve efficiency and reduce wasted gas. Conversion can lower operating costs because a pilot light continuously consumes a small amount of gas.

A qualified HVAC contractor evaluates compatibility, estimates conversion cost, and installs an appropriate ignition kit or recommends a furnace replacement when conversion is impractical.

Cost Considerations And Energy Impact

Pilot lights typically consume between 600 and 1,200 BTU/hour, depending on design. Over a heating season, that continuous use can translate into noticeable gas consumption. Converting to electronic ignition often reduces standby gas use but may involve upfront costs for parts and labor.

Homeowners should compare long-term savings from reduced gas use and potential efficiency gains versus conversion or replacement costs when planning upgrades.

Key Takeaways For Homeowners

• Look For A Gas Control Knob Labeled “Pilot” To confirm a pilot light system.
• Locate A Small Viewing Port Or Flame After powering down the furnace to inspect safely.
• Relight Only If Safe And follow manufacturer instructions; call a professional if unsure.
• Consider Conversion To electronic ignition for efficiency but weigh costs and compatibility.
• Any Gas Odor Is An Emergency—evacuate and call the gas utility.

Additional Resources And Where To Learn More

Manufacturer manuals, local utility provider safety pages, and the Air Conditioning, Heating, and Refrigeration Institute (AHRI) offer reliable guidance on furnace types and safe operation.

For model-specific instructions and parts diagrams, consult the furnace’s data plate and the manufacturer website, or hire an NATE-certified HVAC technician for inspections, repairs, or conversions.